Implication of palladium geometric and electronic structures to hydrogen activation on bulk surfaces and clusters

A great body of theoretical results obtained preferentially with density-functional methods in the last decade is analyzed with emphasis on the relationship between the orientation of the surface for semiinfinite mono-metallic bulk palladium and the cluster-size for finite palladium particles. It is demonstrated that the crystallographic orientation of a surface influences the local electronic structure and the geometric configuration of catalytic centers and this way changes their catalytic properties. Weakly bound molecularly adsorbed states and atomic adsorbates in the most reactive low-coordinated positions are especially sensitive to such changes. The unique feature of small palladium clusters, their ground state magnetism affects mainly the dynamics of dissociative adsorption and leads to the stabilization of pre-dissociated forms of adsorbate. (C) 2001 Elsevier Science B.V. All rights reserved.